Generally speaking, a terminal block includes at least one terminal constituted by a bolt which is made U-shaped by a slot through which the conductor is passed. The conductor is then tightened against the end of the bolt, or against a connection strip, by means of a shoe which slides between the branches of the slotted bolt. When the terminal block includes a plurality of terminals e.g. two or four, the connection strip serves to interconnect them. The shoe comprises the end of a rod which is slidably mounted in a hole in the end of a bell-shaped, tapped cap. A compression spring is interposed between the head of the rod and the cap which is fitted over it, and which compresses it when the cap is screwed onto the bolt. The terminal block generally includes two insulating cheek pieces that are at least as long as the bolt/cap assembly when screwed together. The cheek pieces thus serve to protect the terminal(s) of a terminal block against the danger of short circuits by contact with a terminal, and also make it impossible to use a pair of pliers to screw or unscrew the cap by gripping the body of the cap, or by gripping the top of the cap which usually includes tightening means intended to cooperate with a special spanner or key. Such terminal blocks do not, however, prevent a cap from being screwed on using a key, and the key being removed before the conductor has been properly clamped, where an operator is interrupted in the middle of the job, for example.
Preferred embodiments of the invention provide an electrical connection terminal which positively ensures proper clamping of the electrical conductor.